As shown in FIGS. 24 and 25, in general, a ink-jetting recording head using longitudinal-vibration type of piezoelectric vibrating members comprises a flowing-path unit 101 provided with a lot of nozzles 108 and a lot of pressure chambers 107. The flowing-path unit 101 is stuck onto a head case 102 containing the piezoelectric vibrating members 106.
In detail, the flowing unit 101 consists of a nozzle plate 103 through which the nozzles 108 are formed in two rows, a flowing-path plate 104 through which the pressure chambers 107 respectively communicating with the nozzles 108 are formed and a vibrating plate 105 that seals lower openings of the pressure chambers 107. The nozzle plate 103, the flowing-path plate 104 and the vibrating plate 105 are layered one on top of another as shown in FIGS. 24 and 25. In the flowing-path plate 104, ink reservoir spaces 109 are formed for storing ink that is introduced into the respective pressure chambers 107. In addition, ink paths 110 are formed in the flowing-path plate 104 for connecting the respective pressure chambers 107 and the ink reservoir spaces 109.
The head case 102 is made of a synthetic resin. The head case 102 has vertical through spaces 112. The piezoelectric vibrating members 106 are contained in the spaces 112. Tail ends of the piezoelectric vibrating members 106 are fixed to a fixing plate 111, which is attached to the head case 102. Leading surfaces of the piezoelectric vibrating members 106 are fixed to island portions 105A (see FIG. 25) of the vibrating plate 105, respectively.
When a driving signal generated in a driving circuit 114 is inputted to a piezoelectric vibrating member 106 through a flexible circuit board 113, the piezoelectric vibrating member 106 extends and contracts in a longitudinal direction thereof. When the piezoelectric vibrating member 106 extends and contracts, the corresponding island portion 105A of the vibrating plate 105 vibrates to change a pressure of the ink in the corresponding pressure chamber 107. Thus, the ink in the pressure chamber 107 may be jetted from the corresponding nozzle 108 as a drop of the ink. In addition, as shown in FIG. 24, ink supplying ports 115 for supplying the ink to the ink reservoir spaces 109 are formed through the head case 102 and the vibrating plate 105.
As the flowing-path plate 104 of the flowing-path unit 101, conventionally, a plate formed from a silicon mono-crystal substrate by an anisotropic etching process (see Japanese Patent Laid-Open No. 9-123448), a plate having a layer made of a photosensitive resin, and an electrocasting plate peeled off from a jig substrate (see Japanese Patent Laid-Open No. 6-305142 and Japanese Patent Laid-Open No. 9-300635) may be used.
In a case of forming a flowing-path plate 104 from a silicon mono-crystal substrate by an anisotropic etching process, pressure chambers 107 and ink-paths 110 are formed by the etching process. The etched silicon mono-crystal substrate (flowing-path plate 104) is layered with a metal nozzle plate 103 and a vibrating plate 105 via an adhesive material or the like.
However, in general, a linear expansion coefficient of silicon mono-crystal is different from a linear expansion coefficient of metal. Thus, in the flowing-path unit 101 consisting of the layered plates 103-105, a so-called “warp” may occur. This is not serious in the small-sized recording head, but this may result in difficulty in enlarging the size of the recording head.
In a case of forming a flowing-path plate 104 by layering a photosensitive resin on a substrate, there is a problem that a Young's modulus of the photosensitive resin (flowing-path plate 104) is lower than that of metal or silicon. That is, the photosensitive resin has only a lower rigidity. Thus, if the pressure chambers 107 are arranged more densely, boundary walls therebetween may deform by means of a pressure in an adjacent pressure chamber 107, that is, “cross-talk” may occur. Therefore, in the case, it is difficult to densely arrange the nozzles.
In a case of forming a flowing-path plate 104 by pealing off an electrocasting layer formed on a jig substrate, a “warp” of the electrocasting layer may tend to occur during the peeling off from the jig substrate. That is, dimension accuracy of the flowing-path plate 104 may tend to be lower. In addition, the case needs a step of forming the electrocasting layer on the jig substrate and a step of peeling off the electrocasting layer from the jig substrate, which may result in longer time and greater cost.